Finding out the original MAC address of an interfac

zhjim · 06-29-2009, 12:46 PM

Short version:
How can i find out what mac address had been configured by factory default.
I changed my mac address with

Code:

ip link set addrs 00:01:02:03:04:05

and now want to have the original one back. Any one having any idea?

long version:
Hi folks,

I'm having some trouble with a gigabit LAN PCI Express card. Namely the 89156 from delock. Output of dmesg

Code:

r8169 Gigabit Ethernet driver 2.3LK-NAPI loaded
[    4.137225] r8169 0000:02:00.0: PCI INT A -> GSI 16 (level, low) -> IRQ 16
[    4.137268] r8169 0000:02:00.0: setting latency timer to 64
[    4.137346] r8169 0000:02:00.0: irq 27 for MSI/MSI-X
[    4.137548] eth1: RTL8168b/8111b at 0xf88e2000, 00:01:02:03:04:05, XID 38000000 IRQ 27

So the card was recognized by the kernel. The driver was loaded and everything fine.... should be! But after assigning an ip addr and setting the nic up with

Code:

ip addr add 192.168.1.1/24 dev eth1
ip link set dev eth1 up

the kernel complained about something like that

Code:

?SISTEM? Can't assign address

Also I could not find anything useful on the net finally the readme gave me some. So i changed the MAC address and everything was fine. The nic came up and got an ip through dhclient.

But being nosy i want to know why the old/original mac address didn't work. But even after reboot the new mac address remains. All I know the old one begun with 7b.

So does anybody know how to get the original mac of a nic?
And while your on it. Can you imagine anything why a mac starting with 7b can not be handled by the kernel?

Uncle_Theodore · 06-29-2009, 01:02 PM

The original MAC is written on the card itself...

onebuck · 06-29-2009, 01:54 PM

Hi,

The reason you got a IP after the new MAC was that your original MAC had a assigned IP via the DHCP server previously. That lease had not been released that had been assigned to the MAC. When you changed the MAC and requested a new IP from the server then one was assigned to your device with the new MAC.

BTW, the MAC is unique address assigned to the manufacture to insure no identity conflicts. To arbitrarily assign a MAC to a interface then you can develop problems.

zhjim · 06-29-2009, 02:57 PM

@Uncle: I would need to open the case to get it this way

Absolute right. Sure the easiest thing. Dump me not thinking about it. Thanks

Quote:

Originally Posted by onebuck

Hi,
The reason you got a IP after the new MAC was that your original MAC had a assigned IP via the DHCP server previously. That lease had not been released that had been assigned to the MAC. When you changed the MAC and requested a new IP from the server then one was assigned to your device with the new MAC.

Honestly I'm having trouble understanding what you're saying. Thats how I understand it: I get the old IP back to the new mac cause I got one from the dhcp server with the old mac....

Is that would you wanted to bring across?

Anyway the Problem in first place was that I neither got a IP through dhcp nor through setting one manualy. The card would just not let it be set up with

Code:

ip link set dev eth1 up

ip link also showed a status of DOWN. I could only bring the device up after setting the new mac.

Quote:

Originally Posted by onebuck

BTW, the MAC is unique address assigned to the manufacture to insure no identity conflicts. To arbitrarily assign a MAC to a interface then you can develop problems.

Yup, thats the reason for me trying to get the original back

zhjim · 06-30-2009, 11:33 AM

So debian decided to take on the original mac all by it self after getting on the problem right now.
With this settled heres the marveles error I get with the original mac

Code:

debian:/home/asdf# ip addr
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue state UNKNOWN 
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN qlen 1000
    link/ether 7b:bd:ff:78:eb:fc brd ff:ff:ff:ff:ff:ff
3: eth1_rename: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast state DOWN qlen 1000
    link/ether 00:24:8c:9e:b4:89 brd ff:ff:ff:ff:ff:ff
debian:/home/asdf# dhclient eth0
Internet Systems Consortium DHCP Client V3.1.1
Copyright 2004-2008 Internet Systems Consortium.
All rights reserved.
For info, please visit http://www.isc.org/sw/dhcp/

SIOCSIFFLAGS: Cannot assign requested address
SIOCSIFFLAGS: Cannot assign requested address
Listening on LPF/eth0/7b:bd:ff:78:eb:fc
Sending on   LPF/eth0/7b:bd:ff:78:eb:fc
Sending on   Socket/fallback
receive_packet failed on eth0: Network is down
DHCPDISCOVER on eth0 to 255.255.255.255 port 67 interval 4
send_packet: Network is down

Hm any ideas here? I recall one bits I read on xen networks.
The first two bytes of the mac should be even (or 00) else the mac indicates a mutlicast address..... Probably totaly off track here